linux-kernel - [PATCH] xen/gntdev: fix gntdev

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Message-Id: <20210423054038.26696-1-jgross@suse.com>
Date:   Fri, 23 Apr 2021 07:40:38 +0200
From:   Juergen Gross <jgross@...e.com>
To:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Cc:     Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        stable@...r.kernel.org,
        Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>
Subject: [PATCH] xen/gntdev: fix gntdev_mmap() error exit path

Commit d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert")
introduced an error in gntdev_mmap(): in case the call of
mmu_interval_notifier_insert_locked() fails the exit path should not
call mmu_interval_notifier_remove(), as this might result in NULL
dereferences.

One reason for failure is e.g. a signal pending for the running
process.

Fixes: d3eeb1d77c5d0af ("xen/gntdev: use mmu_interval_notifier_insert")
Cc: stable@...r.kernel.org
Reported-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
Tested-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@...e.com>
---
 drivers/xen/gntdev.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index f01d58c7a042..a3e7be96527d 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -1017,8 +1017,10 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
 		err = mmu_interval_notifier_insert_locked(
 			&map->notifier, vma->vm_mm, vma->vm_start,
 			vma->vm_end - vma->vm_start, &gntdev_mmu_ops);
-		if (err)
+		if (err) {
+			map->vma = NULL;
 			goto out_unlock_put;
+		}
 	}
 	mutex_unlock(&priv->lock);
 
-- 
2.26.2